It can be difficult for Ph.D. students to differentiate between research and non-research. Here I would like to discuss research in terms of contributions. "Contributions" are the key criteria for determining whether your work is worth publishing or not.
There are four key contributions in the BCI field:
1. "New", "non-obvious" artifact: This is kinda obvious. If you introduce new tools/toolset, software/hardware, algorithms, applications, etc., you will be fine here. Just make sure the artifact you created poses some interesting technical challenges. A "new" but "too-easy" artifact is a no-go. For example, simply using SSVEP to turn on/off is a no no....it has no technical challenge! The scientific nature is of engineering. You are likely to earn this contribution.
2. "New", non-obvious, significant knowledge: This is mostly based on experimental studies that expose certain "new" phenomenon or knowledge. Anyhow, new but "common-sense" knowledge is a no-go. The scientific nature is of empirical and rigor. If you truly discover something new (and not obvious), you earn this contribution.
3. "New" methodology: If you propose some new research methodology or "new approach to tackle certain known problems", you earn this contribution. It is quite difficult for new Ph.D. students...in my opinion but it's doable.
4. "New" theory: This is probably the hardest of all contributions. Basically, you are proposing some grand new theory that changes the way we see things. Likely you not gonna work on this level as a Ph.D. student. It takes ones' lifetime to realize one new theory.
A good paper usually composes of ONLY ONE contribution. Having too many contributions confuse your readers. Similarly, lacking any of this contribution will easily allow reviewers to stamp a rejection on your paper.
Another good observation is the keyword "new", which means that novelty is very important in BCI research. Thus, it is useful to regularly ask "Why is this problem so hard?", "Why is this problem worth solving", "What is new in your contributions?"
I hope this starting point helps you guys better plan ahead for your research.
Note: There are other contributions such as doing a large-scale survey, writing an opinionated piece, doing a replication study, etc., but they are rather uncommon, and I believe they are not suitable for any Ph.D. students to pursue these types of contributions. Ph.D. students should focus on the basics.